We are trying to unravel the mechanisms which control the functional properties of spinal cord neurons. We have found that muscle cells grown in culture produce a high molecular weight substance which can enhance the growth of the axons of spinal cord neurons. In this coming year we plan to make more accurate measurements of the chemical properties of this trophic substance. We will use gel filtration and ultracentrifuge sedimentation techniques to obtain measures of its molecular weight. Isoelectric focusing and ion exchange chromotography will be used in determining its isoelectric point. Using these techniques together with affinity chromotagraphy methods we will continue to improve purification methods for this trophic molecule. We will also try to elucidate the mechanism of activation of the slow potassium conductance system found in motoneurons and muscle cells. This year we hope to determine how membrane depolarization and internal calcium contribute to the activation of this conductance system.